Heretofore, there have been industrial processes for producing acetone by dehydrogenating isopropanol and for producing methyl ethyl ketone (MEK) by dehydrogenating sec-butanol in the presence of a solid catalyst. The solid catalyst for such processes is usually zinc oxide or a copper-zinc alloy, and they are used at high temperatures above 400.degree. C. because they are low in activity at low temperatures.
It is reported that the dehydrogenation of alcohols at low temperatures is effectively catalyzed by a copper-complex oxide such as CuO--ZnO, CuO--Cr.sub.2 O.sub.3, and CuO--coO--Cr.sub.2 O.sub.3. However, these catalysts have a drawback in common in that they lose activity very soon and need frequent regeneration. This drawback places them under a practical disadvantage.
Recently an attempt has been made to dehydrogenate an alcohol in the homogeneous liquid phase by using a complex compound of ruthenium or osmium as a catalyst. [Inorg. Chem., 16(1), 137 (1977)] This process, however, has not yet reached the level of practical use.
There is known a process for producing n-decanal by dehydrogenating n-decanol using a ruthenium catalyst supported on alumina. [Gazz. Chim. Ital., 91, 479 (1961)] It is reported that this process is such that the reaction does not proceed when there is no oxygen in the reaction system.
There is also known a process for producing an alicyclic ketone by dehydrogenating an alicyclic alcohol using a ruthenium catalyst supported on a carrier such as carbon or metal oxide although only the former is exemplified (British Pat. No. 849,135). This process has the disadvantage of using essentially carbon as a carrier. The catalyst is easily deactivated by the carrier. Moreover, the catalyst requires a reaction temperature higher than 300.degree. C., at which dehydration and other side reactions take place. For these reasons, this process has not been put to practical use.
The object of the invention is to provide a catalyst that exhibits high catalytic activity at low temperatures and maintains activity for a long time in the process for producing a carbonyl compound by dehydrogenating a lower aliphatic alcohol of 1 to 6 carbon atoms. Applicants found that the object can be achieved by a ruthenium catalyst supported on a carrier.